What is the ruling on someone who wore sewn clothing—such as trousers, for example—out of forgetfulness and only realized it after returning to his country, and what is the ruling if he did so intentionally?

If a pilgrim (muhrim) wears sewn clothing out of forgetfulness, there is nothing upon him. However, if he wears it intentionally, he must offer a fidyah (expiatory sacrifice) and repent if it was without a valid excuse. If it was due to a valid excuse, then only the fidyah is required.